Sensitive indicator



Sept. 19, 1939. C. G, s'ERlGH-r 2,173,487

' SENSITIVE INDICATOR Filed July 20, 1936 Ig L g INVENTOR.

k s g E C' v. @ty/gi; L BY n Q u k )Si s, ATTORNEY Patented Sept. 19, i939 I atrae stares earner erica SENSETIWE ENECA'ER Carl G. Seriglit, Dayton, Ollio, assigner to Bendix Radio Corporation, Baltimore, lvl-d., a corporation of Delaware application .my 2t, rese, serial na eines 2 claims. (ci. rrr- 95;

My invention relates broadly to radio compass field, and a voltage oi like frequency and suitable systems and more particularly to a circuit arphase relationship is also impressed on the armarangement for increasing the eective sensiture, a turning force is imparted to the armativity and damping of the dynamometer type of ture. The direction or' the torque is a function 5 radio compass indicator. of the relationship or' the phases of the field and 5 One of the objects of my invention is to proarmature fluxes. If the armature polarity is revide a means for controlling the phase relationversed with respect to the eld polarity, the Vdiship of the operating currents in the field and rection of the torque is reversed.

armature circuits of the dynamometer type of For any armature position except the zerol radio compass indicator for increasing the efcoupling DOSOll, 2 VOl'ege dile i0 the field flllX l@ iective sensitivity and damping thereof. is induced into the armature circuit. This voltage Another object of my invention is to provide a is a function of the rate of change of current in circuit arrangement for the eld and armature the field coil and will be 90 out of phase with circuits of a visual indicator of the dynamometer the eld current.

l5 type in radio compass systems in which the If the impedance of the armature coil circuit l5 phase angle lead in the armature circuit is conis resistive, there will be no resultant torque but trolled by introducing a predetermined capacity if the impedance is reactive there Will be a torque. in a suitable position in the armature circuit for If the reactance is negative (Capeelfve) the obtaining a condition of optimum sensitivity and torque will oppose the springs, if positive (in damping in operation of the indicator. ductive) the torque will aid the springs tending 20 Still another object of my 'invention is to' proto restore the pointer to the center position.

vide a circuit arrangement for a dynamcmeter' Since the resultant torque opposes the springs type of Visual indicator, having a field winding when the armature circuit impedance is negative,

excited from a modulation generator, and an 'it fOllOWS that a point may be TeaChed Where, i031 armature winding excited from the output of a llCeaSiIlg the lleld Clllel'll and the phase angle 25 signal receiving circuit with means for controlling lead 0f the Current in the armature Circuit by the phase lrelationship of the currents induced making the reaetance more Capaeitative, the in the armature circuit by the field flux with retorque due to this induced current will exceed spect to the currents in the eld circuit for inthat of the springs, and the indiCa'Ol Pointer Will surng a condition of optimum sensitivity and assume its greatest deection the moment its 30 damping during the operation of the visual indiequilibrium in' `the Center POSOD iS disturbed, cater. Without the aid of any signal induced in the Other and further objects of my invention rearmature Circuit DY any Source external t0 the side in the circuit arrangement for controlling the IlClCatOl'.

operation of a dynamometer type of radio eom- For some lower value of ield iiux and/or arma- 35 pass visual indicator as set forth more fully 'in ture CilCllt phase angle lead, the armature Will the specication hereinafter following, by referreturn to the zero position in the absence of a susence to the accompanying drawing, in which: tained external voltage 0f field Supply frequency Figure l diagrammatically and schematically being impressed 011 the armature CTCU- The 4G illustrates one form of radio compass visual in.. maximum usable sensitivity is therefore obtained 40 dicator circuit embodying by invention; Fig. 2 When:

shows a modied form of armature circuit for 1. The highest aVailable ileld Voltage iS l1Sed, the visual indicator system of my invention; and and; Fig. 3 shows a further modified arrangement for 2. The armature Circuit phase angle lead iS .lust the armature circuit in the indicator system 0f short of the value that produces afield induction 45 my invention. torque equal to the restoring torque of the springs. The dynamometer indicator consists in part of In addition, the dYnamOmeer COIIlPaSS meter a neld winding in a magnetic circuit including an contains a metional resistance 0r damping deannular air gap, and an armature coil supported Vice t0 Oppose erratic mOVement 0f the armaon pivots in the air gap and provided with springs ture when transient voltages are applied to the 50 tending to maintain the armature in the position armature circuit. The eicacy of the damper is Where it has zero magnetic coupling to the iield, directly DIOpOrOnal t0 the mOODal resistance this being the normal position of rest indicated of the damper, and inversely proportional to the by zero on the instrument dial. torque necessary to produce a given deflection of Ii an alternating voltage is impressed on the the armature, which is to say inversely propor- 55 tional to the eiective restoring torque of the springs.

It has been shown above that the effective restoring torque of the springs can be reduced by introducing a phase angle lead in the armature circuit. The optimum meter sensitivity is obtained when the eld induction torque resulting from an armature circuit phase angle lead almost equals the spring restoring torque. For any particular value of field flux, the condition for optimum sensitivity' therefore also provides the greatest damping obtainable with that value of field ux, as explained in the preceding. paragraph.

The necessary armature circuit phase angle lead is obtained by connecting a condenser of suitable value 1. In series with the armature.

2. In parallel with the armature, or

3. Across any portion or all of any or all wind ings of transformers or impedances used to couple the armature to its external source of operating voltage.

Referring to the drawing in more detail, I have illustrated the modulation generators which conneet with the field circuit of the visual indicators of the radio compass system as being constituted by pentode tubes I and 2. The pentodes I and 2, respectively, include the grid Ib, shield grid lc, suppressor grid Id, and anode l e; cathode 2a, control grid 2b, shield grid 2c, suppressor grid 2d, and anode 2e. 'Ihe inductance 3 is connected at opposite ends with the control grids Ib and 2b through condensers 4 and 5. 'Ihe inductance 3 is tapped, as indicated at 6 and 1, for supplying the low frequency energy to thecmodulator grids of the modulator tubes in the radio compass circuit. Midtap connection 8 is provided on the inductance 3 and connected with the source of positive potential indicated generally at 9. The midtap 8 is grounded at 30 through a condenser as shown at 3|. Condenser IU serves' as a tuning means for the inductance 3 in the push-pull oscillator circuit. Grid leaks 21 and 28 are connected with ground 29 and to the respective control grids Ib and 2b as shown. Y

The feed-back coupling for the push-pull type of oscillator is obtained by the connection through resistor |I of shield grid Ic to that side of coil 3 which is connected to control grid 2b. Like- Wise, shield grid 2c is connected through resistor I2 to that side of coil 3 which is connected to control grid Ib; the resistors II and I2 constituting a conductive path through coil 3 and center tap 8 to the source of potential 9, andthe shield grids Ic and 2c constituting the anodes of the oscillator system.

It will be seen that the oscillator system is confined to the circuit including the cathode la, control grid Ib, and shield grid Ic of tube I, and cathode 2a, control grid 2b, and shield grid 2c of tube 2, so that low frequency energy may be drawn froml the oscillator by connection to the anodes le and 2c. This connection avoids any tendency of change in frequency of the oscillator under 'influence of change in load in the indicator circuits, so that the system of my invention is particularly adapted for using two or more indicators without impairing the precision operation of the compass. The anode current is supplied to anode Ie from the source of potential 9 and to coil I4 of indicator I5 through connection I6. Likewise, the anode current to anode 2e of tube 2 is supplied from the same source through concathode Ia, controlY vtuning condenser 23.

vthe right or the left.

pointers of indicators |5 and 2|! will, therefore,

nection I6 and coil of indicator I5. Coils I4 and I1 are so connected that the flux in the magnetic circuit I8 of indicator I5, is proportional to the diierence between-the currents in coils I4 and I1.

Inspection will reveal that the potential impressed on control grid Ib of tube I will be the opposite polarity from that potential impressed on control grid 2b of tube 2 at the same instant. It is thus apparent that the .anode current in tube I will increase at the same instant .when the anode current of tube 2 is decreasing, and vice versa in accordance with the frequency of the oscillatory circuit as determined by the characteristics of coil 3 and condenser l0. There will, therefore, be in the magnetic circuit I8 an alter'- nating magnetic lluX corresponding to the frequency of the oscillator.

' I prefer to tune coils I4 and I'I to the frequency of the oscillator by means of condenser I9. This provides the optimum power factor for the circuit constituted by coils |4 and and condenser I9, provides that larger currents of the desired frequency shall flow in these coils, and provides a reduction in the magnitude of undesired currents of harmonic frequencies of the oscillator.

Where it is desirable to repeat the indication on other visual indicators, I arranged the. additional indicators as shown for example by indicator 20 similar in all respects to indicator I5 having actuating coils 2| and 22 connected to anodes le and 2e respectively and associated with Connection 24 which corresponds to the similar connection |6 of indicator I5, may or may not be connected to the source of potential 9. The magnetic circuit 32 of indicator 20 is similar to the magnetic circuit I8 of indicator I5.

The indicators I5 and 20 are of the dynamometer type and each have a movable armature carrying a Winding 25 or 26. The windings 25 and 26 are connected in parallel and connected to the output of the amplifier of the receiver. The normal position of windings 25 and 26 is such that the pointers of indicators I5 and 20 remain in the center of their respective scales in the absence of current in coils 25 and 26, under the influence of sets of spiral springs 33 and 34 connected to opposite ends of the pivot shafts of the pointers. Spiral spring 33, mounted in indicator I5, serves to exert a continuous restoring torque on the pointer of indicator I5, as the indicator I5 is displaced either to the left or to the right. In indicator 20, the spiral spring 34 tends to exert a restoring force on the pointer of indicator 2|), as the indicator 2D is moved either to 'Ihe deection of the be in direction and magnitude proportional to the vector product of the currents in actuating coils I4 and Il and moving coil 25 of indicator I5, and in actuating coils 2| and 22 and moving coil 26 of indicator 20.

Inasmuch as the current in coils 25 and 26 is proportional in magnitude to and controlled in polarity by the signal impressed on the radio compass coil, which in turn is proportional in magnitude to and controlled in polarity by the deviation of the angle of the plane of the radio compass coil from a plane normal to a line to the source of the received signal, it follows that the magnitude of the deflection of indicators I5 and 20 will be a function of the angle of deviation of the radio compass coil from the line to the source 75 of the received signal, and that the direction of said deectio'n will be a function of the direction of the deviation of said compass coil from said line to said source of received signal. I'he ar rangement of the visual indicators is such that changes in condition of load will not influence the constancy of the oscillator frequency.v The condensers I9 and 23 serve to independently tune the associated windings I4 and I1 of indicator I5 and windings 2| and 22 of indicator 20.

In order to secure a proper amature circuit. phase angle lead and consequent eld'induction torque of the desired magnitude and direction, I provide in the circuit associated with the armature, phase determining means. I have indicated the output of thehun-directional receiver of the radio compass receiver terminating at circuit 35, including coupling transformer 3S, having primary winding 31 coupled to secondary winding 3B. Condenser 39 connects across primary winding 31, rendering the output circuit from the receiver selective to the particular tone frequency of the signal, which is the frequency of the modulation generators I and 2. The secondary winding 38 is shunted by potentiometer 40, having an adjustable tap 4I thereon for determining the amplitude of the signal energy supplied to the armature circuit 42. For purposes of adjusting the phase of the current induced in the armature circuit by the field, I introduce, as shown in Figure 1, a condenser 43 of suitable value in series with the armature circuit.

As illustrated in Fig. denser as shown at 44 in parallel with the armature circuit. Y

As illustrated in Fig. 3, I may connect the c ondenser in the position illustrated at 45, that is, across a portion of the tween tap 46 and one end of the secondary winding 38 as shown.

In al1 instances the condensers 43 or 44- or 45 are selected of such value that the degree of phase angle lead introduced in the armature circuit 2, I may connect the con- Y secondary winding 38 beprovides optimum meter sensitivity and damping,

i. e., provides a eld induction torque almost equal to the restoring torque of the springs.

While I have described my invention in certain of its preferred embodiments, I am aware that changes in circuit arrangement may be made and I accordingly desire that it be understood thatK modications may bel made and I intend no limitations upon my invention other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A visual indicator of the dynamometer type comprising a magnetic circuit, an angularly movable armature disposed in said magnetic circuit,

spring means for normally maintaining said ar` mature in a predetermined position, a field winding'associated with said magnetic circuit, an armature'windlng carried by said armature, means for impressing a single exciting current on said field winding, said current being oscillatory ata fixed frequency, means for impressing signal currents on said armature winding, and a capacitati've reactance connected in series with said armature winding for introducing a phase angle lead of the current induced therein by the field with respect to the field current.

2. A visual indicator of the dynamometer type comprising a magnetic circuit, an angularly movable armature disposed in said magnetic circuit, spring means for normally maintaining said armature in a predetermined position, a field winding associated with said magnetic circuit, an armature winding carried by said armature,

' means for impressing a single exciting current on said eld winding, said current being oscillatory at a fixed frequency, means for impressing signal currents on said capacitative reactance connected in circuit with said armature winding for introducing a phase angle lead of the current induced therein by the field with respect to the eld current.

- CARL G. SERIGHT.

armature winding, .and a. 

